1. Field of the Invention
The present invention relates to a method for manufacturing a plastic fuel tank that includes a connector provided with a screw thread. It also relates to a fuel tank that can be obtained by this method.
2. Description of The Related Art
Fuel tanks (FTs) on board vehicles of various kinds generally have to meet imperviousness and permeability standards in relation to the type of use for which they are designed and the environmental requirements that they have to satisfy. Both in Europe and throughout the world we are currently experiencing a considerable tightening of the requirements concerned with limiting the emissions of pollutants into the atmosphere and into the environment in general. The design of fuel tanks is therefore evolving quickly towards techniques capable of better guaranteeing the imperviousness and safety under varying conditions of use. Furthermore, attempts are also being made to minimize the losses originating from the pipes and various accessories connected to the tanks. A means sometimes used has been to incorporate certain accessories and pipes inside the tanks, thus eliminating their interface with the external atmosphere. Preferably, these elements are fastened to the internal wall of the tank and do not pass through it, so as to avoid damaging the barrier layer often present in these tanks and to eliminate the risk of leaks due to the use of sealing devices.
Patent EP 875411 in the name of the Applicant proposes a means of fastening accessories inside a plastic FT by taking advantage of the molten state of the plastic while it is being moulded, which consists in producing a relief in its wall so as to fasten thereto a pump/gauge module provided with a corresponding relief during a finishing operation after the moulding. This relief consists in fact of a dovetail, thereby implying a small volume in the region of the fastening point (in order to be able to slide the component into the relief) and the use of an additional piece or chock for securing/blocking the fastening.
Patent application WO 2006/008308 in the name of the Applicant discloses a method for manufacturing a plastic FT by profiting from the fact that a parison is molten while it is being moulded, in order to fasten accessories directly to it, a core being used to do this. In this method, the accessory is fastened to the parison by snap-riveting, that is to say by the in situ formation of a molten plastic rivet, which is forced through an orifice and left therein to solidify. However, this method entails a residence at high temperature and possibly at high pressure (if the moulding takes place by blow moulding), something which certain “fragile” accessories cannot tolerate from this standpoint. Furthermore, certain accessories are too heavy to be attached hot (there is a risk of deforming the parison). Finally, the fastening obtained is permanent, i.e. it cannot be removed without damaging the tank and/or the component.